Poor anticoagulation control in patients taking warfarin at a tertiary and district-level prothrombin clinic in Cape Town, South Africa

Ebrahim, Ismaeel; Bryer, Alan; Cohen, Karen; Mouton, Johannes P.; Msemburi, William; Blockman, Marc

doi:10.7196/samj.2018.v108i6.13062

Cited by 22 publications

(48 citation statements)

References 17 publications

(24 reference statements)

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“…This occurred despite regular INR monitoring. Unfortunately, our findings complement other recent sub-Saharan studies in South Africa, Namibia and Botswana, all reporting poor INR control, with mean/median TTR ranging from 29% to 47% [1,12,13]. It is known that a higher TTR is associated with increased efficacy of warfarin and reduction in bleeding complications [14].…”

Section: Discussionsupporting

confidence: 83%

“…Under-dosing (leading to a sub-therapeutic INR) and overdosing (leading to a supra-therapeutic INR) places individuals at risk of thrombosis and bleeding, respectively. INR control in patients in sub-Saharan Africa is often poor [1][2][3] which may result in potentially preventable morbidity [4] and mortality [5]. The burden of HIV and tuberculosis (TB) is high in sub-Saharan Africa [6].…”

Section: Introductionmentioning

confidence: 99%

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A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa

et al. 2020

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Introduction Warfarin is the most commonly prescribed oral anticoagulant in sub-Saharan Africa and requires ongoing monitoring. The burden of both infectious diseases and non-communicable diseases is high and medicines used to treat comorbidities may interact with warfarin. We describe service provision, patient characteristics, and anticoagulation control at selected anticoagulation clinics in Uganda and South Africa. Methods We evaluated two outpatient anticoagulation services in Kampala, Uganda and three in Cape Town, South Africa between 1 January and 31 July 2018. We collected information from key staff members about the clinics' service provision and extracted demographic and clinical data from a sample of patients' clinic records. We calculated time in therapeutic range (TTR) over the most recent 3-month period using the Rosendaal interpolation method. Results We included three tertiary level, one secondary level and one primary level anticoagulation service, seeing between 30 and 800 patients per month. Care was rendered by nurses, medical officers, and specialists. All healthcare facilities had on-site pharmacies; laboratory INR testing was off-site at two. Three clinics used warfarin dose-adjustment protocols; these were not validated for local use. We reviewed 229 patient clinical records. Most common indications for warfarin were venous thrombo-embolism in 112/229 (49%), atrial

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa

et al. 2020

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“…2%) and about half of them were prospective (Table S1). The remaining articles (n = 10) presented information on the trends in mortality attributed to AF using modeling analysis, and on the cost of AF treatment, anticoagulation utilization, and monitoring …”

Section: Resultsmentioning

confidence: 99%

“…The remaining articles (n = 10) presented information on the trends in mortality attributed to AF using modeling analysis, 79 and on the cost of AF treatment, anticoagulation utilization, and monitoring. [80][81][82][83][84][85][86][87][88] 3.1 | Prevalence of AF in community-based and hospital-based studies Only three studies reported the prevalence of AF in the general population in the community. [17][18][19] This prevalence was 4.3%, 0.3%, and 0.7% in individuals aged ≥40 years, 17 aged ≥50 years, 18 and aged ≥70 years 19 in Ethiopia, Ghana, and Tanzania, respectively ( Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…Few studies reported primary mortality data in patients with AF, 20,67,70,[74][75][76] most of them lacking information on the time of permanent AF was the most common. From studies reporting on antivitamin K anticoagulation, [79][80][81][82][83][84] AF was the most common indication, along with a mechanical valve (Table S4). In all studies presenting data on thromboembolic risk and antithrombotic therapy use, at least 80% of patients had an indication of anticoagulation based on the CHADS 2 or CHA 2 DS 2 VASC scores.…”

Section: Complications Of Afmentioning

confidence: 99%

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A review of the epidemiology of atrial fibrillation in sub‐Saharan Africa

Noubiap

Nyaga²

2019

Cardiovasc electrophysiol

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This systematic review summarizes the data on the prevalence, risk factors, complications, and management of atrial fibrillation (AF) in sub‐Saharan Africa (SSA). Bibliographic databases were searched from inception to 31 May 2019, to identify all published studies providing data on AF in populations living in SSA. A total of 72 studies were included. The community‐based prevalence of AF was 4.3% and 0.7% in individuals aged ≥40 years and aged ≥70 years, respectively. The prevalence of AF ranged between 6.7% and 34.8% in patients with ischemic stroke, between 9.5% and 46.8% in those with rheumatic heart disease (RHD), between 5% and 31.5% in patients with dilated cardiomyopathy. The main risk factors for AF were hypertension, affecting at least one‐third of patients with AF, and valvular heart disease (12.3%‐44.4%) and cardiomyopathy (~20%). Complications of AF included heart failure in about two thirds and stroke in 10% to 15% of cases. The use of anticoagulation for stroke prevention was suboptimal. Rate control was the most frequent therapeutic strategy, used in approximately 65% to 95% of AF patients, with approximately 80% of them achieving rate control. The management of AF was associated with exorbitant cost. In conclusion, AF seems to have a higher prevalence in the general population than previously thought and is mostly associated with hypertension, cardiomyopathy, and RHD in SSA. It is associated with a high incidence of heart failure and stroke. The management of AF is suboptimal in SSA, especially with a low uptake of oral anticoagulation.

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Developing and Validating a Clinical Warfarin Dose‐Initiation Model for Black‐African Patients in South Africa and Uganda

Asiimwe

Waitt

Sekaggya-Wiltshire

et al. 2020

Clin Pharma and Therapeutics

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Warfarin remains the oral anticoagulant of choice in sub-Saharan Africa. However, dosing is challenging due to a highly variable clinical response for a given dose. This study aimed to develop and validate a clinical warfarin doseinitiation model in sub-Saharan Black-African patients. For the development cohort, we used data from 364 patients who were recruited from 8 outpatient clinics and hospital departments in Uganda and South Africa (June 2018-July 2019). Validation was undertaken using the International Warfarin Pharmacogenetics Consortium (IWPC) dataset (690 black patients). Four predictors (age, weight, target International Normalized Ratio range, and HIV status) were included in the final model, which achieved mean absolute errors (MAEs; mean of absolute differences between true dose and dose predicted by the model) of 11.6 (95% confidence interval (CI) 10.4-12.8) and 12.5 (95% CI 11.6-13.4) mg/week in the development and validation cohorts, respectively. Two other clinical models, IWPC and Gage, respectively, obtained MAEs of 12.5 (95% CI 11.3-13.7) and 12.7 (95% CI 11.5-13.8) mg/week in the development cohort, and 12.1 (95% CI 11.2-13.0) and 12.2 (95% CI 11.4-13.1) mg/week in the validation cohort. Compared with fixed dose-initiation, our model decreased the percentage of patients at high risk of suboptimal anticoagulation by 7.5% (1.5-13.7%) and 11.9% (7.1-16.8%) in the development and validation cohorts, respectively. The clinical utility of this model will be tested in a prospective study.

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Poor anticoagulation control in patients taking warfarin at a tertiary and district-level prothrombin clinic in Cape Town, South Africa

Cited by 22 publications

References 17 publications

A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa

A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa

A review of the epidemiology of atrial fibrillation in sub‐Saharan Africa

Developing and Validating a Clinical Warfarin Dose‐Initiation Model for Black‐African Patients in South Africa and Uganda

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